Optical light pens of the type disclosed in this application find use in "reading" coded information appearing on the label of an item. If the items are sold in a retail store, the person who checks out the item has such an optical pen which is pressed against the label and moved along the coded information on the label. The pen "reads" the code and provides input to a computer terminal representative of the code. Such terminal may produce a printed tape for the customer, inventory information for a remotely located computer, etc.
One type of code suitable for retail stores consists of a set of nonreflecting bars on a reflecting label (or alternatively reflecting bars on a nonreflecting label). A bar pattern is established to correspond to each of the ten basic numerals.
Such optical pens typically have a light source which generates light intended to strike the region of the code. When the light strikes a nonreflecting bar, no light is reflected, while, if the light strikes a reflecting bar, light is reflected back into the pen. Thus, by moving the pen across the bar pattern, light fluctuations are produced, representative of the presence and absence of bars and their respective widths. The reflected light is sensed by a detector which converts the light information into electrical signals for further processing by the computer terminal.
Presently available light pens use an incandescent lamp as the light source. Disadvantages associated with the use of such a source are limited life of the lamp, heat generation which is detrimental to the pen components and uncomfortable for its user, substantial energy requirements to energize the lamp, and the need to exercise extreme care in handling the pen because of the fragile nature of the lamp filament.